The present invention relates to fusion splicing of optical fibers and more particularly, the present invention relates to a structured arc technique using a focusing sleeve for focusing the electric arc used to fuse optical fibers.
A preferred technique for permanently joining two optical fibers utilizes a fusion splice. A fusion splice is created by localized heating of the ends of the two optical fibers to be joined. Since optical fibers are generally made from multi-component glass, quartz, synthetic resins and/or other material, the localized heating causes the two fiber ends to xe2x80x9cfusexe2x80x9d together. This results in a continuous length of material with minimum discontinuities and/or reflections at the splice point. One of the most commonly known heating source utilized to fuse the fibers together is an electric arc. However, other techniques, for example, a micro-flame or a CO2 lasers may also be used.
FIGS. 1-4 show a prior art technique related to fusion splicing of optical fibers. FIG. 1 shows a basic configuration that is used for fusion splicing two optical fibers using an electric arc. Individual fibers 101 and 102 are carefully prepared by removing, for example, outer cable jackets, buffer tubing, primary coating placed directly on the fibers and/or other protective material. Each fiber is carefully cleaned and perpendicularly cleaved to form a perpendicular edge. The fibers are placed and secured in a jig that is comprised of movable plates 103 and 104. The plates have a vee-grove 105 for retaining the optical fibers. A mechanical clasp or similar mechanical fastener may be used to prevent the fibers from becoming mis-aligned. The configuration further includes electrodes 106 and 107 for producing an electrical arc. As shown, electrode 107 is connected to the positive side of the high voltage arc supply 108 and electrode 106 is connected to the negative side of the high voltage arc supply 108.
FIGS. 2a-c show the operation of the basic configuration of FIG. 1. Initially the fibers 101 and 102 are separated by a short gap and are aligned so that their cores are matched together, as shown in FIG. 2a. As shown in FIG. 2b, a brief electric arc discharge may be applied at the splicing point at the so that surface defects, imperfect fiber end preparation such as burrs or lip, are eliminated. The fibers are subsequently butted together and a constant electrical arc 110 is applied via the electrodes 107 and 106, as shown in FIG. 2c. The electric arc 110 is formed by a large flow of electrons from the positive electrode 107 to the negative electrode 106. The high voltage required to create the electric arc 110 is supplied by the high voltage arc supply 108. The intense heat generated by the high voltage electric arc 110 at the splice point causes the fibers to fuse together and generally the fiber cores are matched as closely as possible. If the preparation, alignment and arc 110 discharge occur properly, the result may be a continuous fiber strand with minimum losses at the splice points.
Problems associated with using a high voltage electric arc 110 for the heat source are shown in FIGS. 3 and 4. After use, grunge and/or carbon deposits 301 can build up on the tips of the electrodes 106 and 107. The grunge and/or carbon deposit buildup 301 and 302 can cause the position and/or the intensity of the electric arc 110 to vary. As shown in FIG. 3, if the grunge buildup 301 is heavier on one side of the electrodes, this may result in the initial formation of an uneven electric arc 110 which may prevent the proper heating required to form a desirable splice. For example, the fiber cores may not fuse together properly resulting in an undesirable splice with increased losses at the splice points.
As shown in FIG. 4, if the grunge buildup 301 is on both sides, then initially the electric arc may not be of the desired intensity required for a proper fusion splice. In addition, as the grunge is burned off, then the intensity of the arc may increase as the voltage across the electrode remains constant since the grunge is more transmissive than air. Thus, again resulting in the possibility of an undesirable splice.
Due to carbon/grunge deposits, an operator may spend increased time in constantly cleaning the electrode tips. In addition, there is a possibility that the electrode tips may be damaged due to the deposit buildup or during cleaning of the electrodes. Although the intensity of electrical arc 110 may be controlled by varying the voltage on the high voltage arc supply 108, controlling the shape or focusing the intensity of the electrical arc 110 may not be possible using conventional techniques. For example, it may desirable to narrow the electrical arc 110 for focused heating at a splice point. In the alternative, it may be desirable to increase the width to reduce the heat generated at the splice point.
This problem can be magnified when the fusion-splicing device is used for simultaneously fusing a plurality of optical fibers. Such a device is commonly called a mass fusion splicer. In a mass fusion splicer, an imperfect arc caused by grunge or buildup 301 can cause some of the fibers not to fuse properly. In addition, it may further be desirable to control the electrical arc for focused heating, for example, while performing the mass splice.
However, no conventional techniques are known to exist that permit the electric arc in a fusion splicer to be controlled such that the effects of deposit buildup may be eliminated.
What is needed is an apparatus and method for fusion splicing optical fibers that prevents the formation of an uneven electrical arc at a splice point so that a proper fiber optic splice may be formed. What is also needed is a method and apparatus for fusion splicing optical fibers that minimizes the effect of grunge and/or deposits on electrode tips such that cleaning of the electrode tips may be reduced or even eliminated. What is further needed is a way of controlling the shape of the electric arc for increasing and/or decreasing the focus of heat intensity at a particular location.
The present invention introduces an arc shaping member to be used in fiber optic fusion splicers. The use of the arc shaping member, referred to herein as a focusing sleeve, may minimize the undesirable effects of grunge and/or deposits than can buildup on arc electrodes. The buildup of grunge or other deposits can cause formation of an irregular electrical arc possibly resulting in an undesirable splice. In a fiber optic splicer, a focusing sleeve may be mounted in a plane parallel to the optical fibers being spliced and in a plane perpendicular to the arc electrodes. The focusing sleeve may be installed such that the sleeve surrounds the electric arc created by the arc electrodes. The presence of the focusing sleeve causes the electric arc to maintain the desired shape and/or intensity. The present invention may reduce the effect of grunge and/or carbon or other such deposits on the electrode tips such that cleaning of the electrode tips may be reduced or even become unnecessary. Embodiments of present invention may further permit an operator to control, independent of the arc voltage, the shape, size and heat intensity of the electrical arc. The shape of the electric arc may be controlled for increasing and/or decreasing the focus of heat intensity at a desired location.
In embodiments of the present invention, the focusing sleeve may be mounted on one or both sides of the optical fibers. The focusing sleeve may be made out of a plurality of differing materials, for example, gold, platinum, tungsten, rhodium and/or other suitable material. The focusing sleeve(s) may be removably attached to a holder for holding the sleeve(s) in the desirable position. In embodiments of the present invention, the holder may be slidably coupled to a rail such that the position of the holder and/or focusing sleeves may be variable. In embodiments of the present invention, the size, shape and location of the focusing sleeve(s) may be variable so that the shape of the electric arc may be controlled, independent of the arc current or voltage. In an alternative embodiment, the arc shaping member can be in the form of a substantially completed ring having first and second ends. The ends may be connected to a voltage supply to control the focus of the electric arc.
Although the invention has been defined using the appended claims, these claims are exemplary and limiting to the extent that the invention is meant to include one or more elements from the apparatus and methods described herein. Accordingly, there are any number of alternative combinations for defining the invention, which incorporate one or more elements from the specification (including the drawings, and claims) in any combinations or subcombinations.